The thermal evolution of the western equatorial Pacific warm pool during the Pleistocene and late Pliocene epochs

The late Pliocene and Pleistocene epochs have been characterized by a series of climate cycles generally referred to as ice ages. The ice ages not only involved high latitude climate oscillations as this designation implies, but also variability in low latitude tropical climate. A number of studies, including the series presented in this document, support a relatively novel perspective of the ice ages. This "low-latitude" perspective is based on recent observations that suggest that not only did the tropics experienced clear climatic cycles during the glaciations, but also that tropical climate changes preceded those in continental ice volume by several thousand years.; This thesis dissertation focused on reconstructing the temperature and hydrological evolution of the western equatorial Pacific (WEP) warm pool over the late Pliocene (2.3 to 3.1 Ma) and Pleistocene (1.3 to 0.45 Ma) Epochs using the foraminiferal Mg/Ca Paleothermometry technique and foraminiferal oxygen isotopes. Climate reconstructions are based on sediments from Ocean Drilling Program (ODP) Hole 806B on the Ontong Java Plateau, a site regarded to have remarkably constant sedimentation rates and very good foraminiferal preservation.; These records indicate that: (1) during the Pleistocene, WEP warm pool sea surface temperature (SST) cycles switched from a dominant period of 41 ky before ∼950,000 (ky) to a period of ∼100 ky after this time; (2) Pleistocene and Late Pliocene SST cycles in the WEP warm pool are synchronous and have a similar magnitude to SST cycles in the eastern equatorial Pacific cold tongue; (3) equatorial Pacific SST cycles precede continental ice volume changes by several thousand years during the late Pliocene and Pleistocene Epochs and; (4) a marked east-west equatorial Pacific zonal temperature gradient existed during the Late Pliocene, in contrast with previous inferences. The character of tropical Pacific climate evolution, suggests that variability in radiative forcing by atmospheric greenhouse gases and the associated feedbacks (i.e. water vapor, ice albedo, etc.) played a major role in driving tropical climate evolution on glacial to interglacial time scales during the late Pliocene and Pleistocene epochs.